Preheat the oven to Gas Mark 8, 230°C (450°F). Halve the potatoes and place in a pot of water. Bring to the boil for 6 to 8 minutes until nearly done. Remove the water and drain well. Peel the carrots and courgette and cut them lengthwise into 4. If the carrots are large, cut them in half again. Cut the scallions into 4 cm pieces. Peel and chop the garlic. Zest the lemon. Halve the chicken breast lengthwise and season with salt and pepper. Take a piece of baking paper/aluminium foil for the vegetables and put in a baking dish, make one papillote per person. Spoon the boiled potatoes, carrots, courgette, scallions, olives, lemon zest, pieces of chicken and sprig of thyme into each papillote. Fold the papillote together but leave it open at the top. Mix the chicken stock, lemon juice and garlic and pour into the papillote. Pour oil on top and season with freshly ground pepper. Close the papillote and place in the middle of the oven for 25 to 30 minutes until the chicken and vegetables are al dente. Serve immediately! Tip Use white wine instead of chicken stock. Do not add lemon juice and season with salt and pepper.